In certain high power RF applications, pulsed RF power is needed at multiple different loads at different times. For delivery to n loads, this may be implemented using n separate sources and transmission lines, with appropriately coordinated timing. Rather than having each source connected to a single load, another approach is to use phase directed combining to send power from multiple sources to a selected one of the desired loads, allowing power to be sequentially routed to different individual loads by changing the input phases. This approach allows the peak power requirement to be reduced by roughly a factor of n. It may be implemented using a high power RF switching circuit. For example, four-port hybrids may be used for combining power in waveguide by controlling the relative phase of the inputs to selectively direct power out of either output.
As shown in FIG. 1, a traditional 2×2 waveguide hybrid has a pair of rectangular waveguides joined to allow matched directional coupling. This particular “magic-H” configuration, originated by the inventors, has mitred bends at all four ports and appropriate adjustment of the dual-moded width section to allow combining the input power at the two right ports 102, 106 to be selectively directed to one of the two left output ports 100, 104. Removal of sharp-edged wall apertures, which can be prone to breakdown, makes this geometry eminently suited for use in high power applications. It also avoids the use of posts, common in magic-Ts. The waveguide height of this 2-D design can be raised to further increase power handling. Note that this H-plane geometry can be employed to design couplers with arbitrary power division. The figure shading indicates the electric field strength for a particular example where 9.3 GHz power is directed from the right input ports 102, 106 to the left output port 104. The fields at the input ports 102, 106 are 90° out of phase.
If the port widths are constrained to be half the center width and the mitres 45°, the particular symmetry of the 2×2 hybrid design of FIG. 1 allows it to be merged with three other 2×2 hybrids radially arranged to create an 8-port 4×4 “cross potent” superhybrid waveguide circuit, as shown in FIG. 2. The resulting 8-port device has four input ports (a pair of ports 200, 202 on the top and a pair of opposite ports 204, 206 on the bottom) and four output ports (a pair of ports 208, 210 on the left and a pair of opposite ports 212, 214 on the right). RF power input at the four input ports can be combined and directed by proper phase control to any one of the four output ports on the orthogonal arms. This 4×4 design is the equivalent of four hybrids with ports properly joined. For more convenient flange connections and to accommodate maintaining symmetry through the overmoded regions, asymmetric H-plane bend/tapers (e.g., asymmetric H-plane bend taper 216) to standard waveguide width are appended to the cross-potent ports in the figure. The figure shading indicates the electric field strength for an example in which RF power from the input ports 200, 202, 204, 206 is directed to the upper left output port 208 through the selection of appropriate phases of the RF signals at the input ports.
Note that the 4×4 design superhybrid, like the 2×2 hybrid design, has its waveguides all in a common plane (the H-plane). A straightforward extension in the plane of this 4×4 8-port device to 8×8 16-port device or 16×16 32-port device, however, leads to increasingly complicated and extensive layouts, requiring many bends and waveguide runs to connect component ports.